Project Summary/Abstract Mitochondria are the major source of cellular energy and are also one of the major sites of defects leading to age-related disorders. In spite of the obvious importance, roughly 1/3 of the proteins found there have no know function. One major goal of the Rutter laboratory is to define the functions of a subset of these proteins, particularly those that are highly evolutionarily conserved across eukaryotic species. We have begun this process and have defined the molecular functions of ten mitochondrial protein families. These have included important factors for OXPHOS complex assembly, mitochondrial quality control, metabolic regulation and others. These discoveries have enabled our laboratory and many others to develop new understanding of normal human physiology and disease pathophysiology, including the discovery of two new human disease genes. The proposed future activities are a combination of continuing our efforts to define the functions of previously unstudied mitochondrial proteins and leveraging our previous discoveries toward a better understanding of mitochondrial biology and its physiological manifestations.